Infectious disease adversely affects livestock production and animal welfare, and often has major impacts upon human health and public perception of livestock production. For example, the costs of existing endemic diseases are estimated as 17% of turnover of livestock industries in the developed world and 35-50% in the developing world. Furthermore, epidemics, particularly in the developed countries, incur further major costs and profound impacts upon the rural economy and on public confidence in livestock production. Biomolecular approaches to enhance the underlying genetic ability of an animal to combat infectious disease will enhance animal production regimes. Such technologies, along with traditional disease control measures, will enable more effective and sustainable disease control.
Central to the immune response a mammal activates up pathogen infection is the gene transcription pathway utilising the transcription factor NFkappaB, which is an obligate dimer protein. This transcription factor regulates, amongst other signalling pathways, the pathogen induced cytokine response that is central to the animal's immune response upon infection. The predominant components of the NFkappaB dimer are the RELA (p65) and NFKB1 proteins. The RELA protein is encoded by a gene which displays polymorphic variation within pig species. In particular African and Eurasian pigs display different allelic versions of RELA and functional studies indicate that the African RELA variant displays a reduced NFkappaB activity that is generally equivalent to the animal carrying only one copy of the ‘Eurasian’ gene. It is known from mouse studies that animals that carry a single copy of the RELA gene are viable.
Pigs succumb to many pathogens including a typically lethal haemorrhagic fever due to infection by ASFV. African swine fever is a highly infectious disease of domestic pigs, with virulent isolates causing a rapid fatal haemorrhagic fever. However, in contrast to domestic pigs, the porcine species native to Africa tolerate infection.
ASFV is notifiable to the World Organization for Animal Health (OIE), placing it in the highest category of infectious animal pathogens. It exhibits remarkable potential for transboundary spread, and outbreaks in domestic pig populations have a serious socioeconomic impact worldwide. Furthermore, ASF is considered to be the major limiting factor to pig production in Africa. ASFV is a large, double-stranded DNA virus and the only member of the Asfarviridae family, suggesting that it may carry novel genes that are not carried by other virus families. The ability of the virus to persist in one host while killing another genetically related host implies that disease severity may be, at least in part, modulated by host genetic variation. Such viruses attempt to evade the host immune response through the action of virus-encoded immune modulators. ASFV encodes several such factors, one of which interacts with the NFAT and NFkappaB signalling pathways. Sequencing of components of these pathways has indicated a very high degree of homology between pig species except in the sequence of RELA. In particular, allelic variation exists within the gene sequence encoding the transactivation domains of RELA. Palgrave et al. (Journal of Virology, June 2011, p. 6008-6014, Vol. 85, No. 12), which is incorporated herein by reference, describes polymorphisms in the RELA gene which seem to correlate with increased tolerance to ASFV in warthogs.
Such variation in RELA is notable given the absence of sequence variation that exists in other components of the NFkappaB and similar pathways between pig species, for example PPIA, NFATC1 regulatory domain and NFKBIA genes.
The present invention provides a genetically edited animal that has altered RELA expression or activity. These animals can be generated by an efficient biomolecular approach utilising genome editing technology. Differences in NFkappaB activity that reflect the level of p65 activity are likely to affect how an individual animal responds to pathogen challenge and to other forms of biological stress or insult. In particular, this genetic variation is highly likely to impact on how pigs respond to ASFV and, potentially, other viruses in addition to infection by other forms of pathogen. Additionally, animals with altered NFkappaB levels or activity are likely to exhibit marked difference in chronic and autoimmune disease severity.